So if your carrier says “you have long PDD” then you want to decrease the PDD. As I said, there is really 0 pdd in the tenor. PDD is post dial delay, the time of silence the caller hears from the time they are done dialing till they hear ring back.
From the tenor, it adds almost 0 time to this. As soon as the call comes to the tenor it is immediately sent out the FXO. It must dial digits to the GSM, so that will take a little time to dial each digit, but you cannot speed this up. The delay is usually on the GSM and wireless network in the time it takes to receive the digits, send it over the wireless network and make the connection.